Vehicle-occupant fatigue-level assessment method, vehicle seat assessment method, and vehicle seat assessment device

ABSTRACT

A highly reliable vehicle driver&#39;s fatigue evaluating method is provided, which is capable of quantitatively calculating a degree of fatigue of a driver seated on a seat. The degree of fatigue of the driver seated on a seat is quantitatively calculated based on an amount of rearward deflection of a lower part of a backrest portion of the seat, a load applied downward to a front part of a seating portion of the seat, and a load applied rearward to an upper part of the backrest portion, in a state of the driver being seated on the seat.

TECHNICAL FIELD

The present invention relates to a vehicle driver's fatigue evaluatingmethod for evaluating a degree of fatigue of a driver sitting on a seatof a vehicle such as a passenger vehicle, commercial vehicle or a bus,and to a vehicle seat evaluating method and vehicle seat evaluatingapparatus using this vehicle driver's fatigue evaluating method.

BACKGROUND ART

In order to improve comfort in vehicles, development is desired of seatsthat cause little fatigue after a long sitting. To reduce the fatigue ofthe waist in particular is effective for relieving the fatigue of thewhole body for the driver sitting on the seat.

The vehicle driver's fatigue evaluating method includes a method inwhich a subject is asked to enter a feeling of seating and a feeling offatigue (especially a feeling of fatigue of the waist) on an evaluationsheet, and a method in which the fatigue of the waist of a subject isevaluated by detecting the myoelectric potential of the waist, bothafter the subject is actually seated on a seat for a long time.

As described in the prior art, a problem of low reliability occurs withthe method in which the subject is asked to enter a feeling of seatingand a feeling of fatigue on an evaluation sheet. This is because thesubject's subjectivity tends to influence the evaluation of the feelingof seating and the feeling of fatigue (especially a feeling of fatigueof the waist), and an objective and quantitative evaluation of thefatigue of the driver sitting on a seat is impossible.

In the method in which the fatigue of the waist of a subject isevaluated by detecting the myoelectric potential of the waist, themyoelectric potential detected is prone to noise (spike noise, i.e.noise of very small pulse width resulting from switching operations).The fatigue of the driver sitting on a seat cannot be evaluated properlyonly by detecting the myoelectric potential of the subject's waist.Further, its validity is not positive with respect to the existence ofcorrelation between the fatigue of the driver sitting on the seat andthe myoelectric potential of the subject's waist.

The object of the present invention is to provide a highly reliablevehicle driver's fatigue evaluating method capable of quantitativelycalculating a degree of fatigue of a driver seated on a seat, and toprovide a highly reliable vehicle seat evaluating method and vehicleseat evaluating apparatus using this vehicle driver's fatigue evaluatingmethod.

DISCLOSURE OF THE INVENTION

[I]

According to a first characteristic feature of the present invention, avehicle driver's fatigue evaluating method is provided forquantitatively calculating a degree of fatigue of a driver seated on aseat based on an amount of rearward deflection of a lower part of abackrest portion of the seat, a load applied downward to a front part ofa seating portion of the seat, and a load applied rearward to an upperpart of the backrest portion, in a state of the driver being seated onthe seat.

In quantitatively calculating a degree of fatigue of the driver seatedon the seat, detection values other than a subjective evaluation by asubject and a myoelectric potential of the waist of the subject includea load applied rearward to an upper part of the backrest portion, a loadapplied rearward to an intermediate part of the backrest portion, a loadapplied rearward to a lower part of the backrest portion, an amount ofrearward deflection of the upper part of the backrest portion, an amountof rearward deflection of the intermediate part of the backrest portion,an amount of rearward deflection of the lower part of the backrestportion, a load applied downward to a front part of the seating portion,a load applied downward to an intermediate part of the seating portion,a load applied downward to a rear part of the seating portion, an amountof downward deflection of the front part of the seating portion, anamount of downward deflection of the intermediate part of the seatingportion, and an amount of downward deflection of the rear part of theseating portion.

Experiments carried out by Applicant herein have shown that, among theabove detection values, the three detection values, i.e. the amount ofrearward deflection of the lower part of the backrest portion, the loadapplied downward to the front part of the seating portion and the loadapplied backward to the upper part of the backrest portion, greatlyinfluence the degree of fatigue of the driver seated on the seat.

These amounts of deflection and loads are free from the subject'ssubjectivity. Since the amounts of deflection of the seat and the loadsapplied to the seat, which are not a subject, are detected, noise (spikenoise) will not occur. Thus, a highly reliable vehicle driver's fatigueevaluating method is provided according to this characteristic feature.

[II]

According to a second characteristic feature of the present invention,the degree of fatigue of the driver seated on the seat is calculatedquantitatively by using an operational expression determined by astatistical technique.

According to this characteristic feature, the degree of fatigue of thedriver seated on the seat may be obtained properly by adopting amultivariable function of the degree of fatigue of the driver seated onthe seat, using the amount of rearward deflection of the lower part ofthe backrest portion, the load applied downward to the front part of theseating portion and the load applied backward to the upper part of thebackrest portion as variables.

[III]

According to a third characteristic feature of the present invention,the operational expression noted in section [II] above is obtained by amultiple regression analysis with the amount of rearward deflection ofthe lower part of the backrest portion, the load applied downward to thefront part of the seating portion and the load applied rearward to theupper part of the backrest portion regarded as explanatory variables,and an actual degree of fatigue measured of the driver seated on theseat as a response variable.

Multiple regression analysis is a typical example of the operationalexpression determined by statistical technique. A highly reliableoperational expression is obtained by selecting detection values givinga high contribution, i.e. the amount of rearward deflection of the lowerpart of the backrest portion, the load applied downward to the frontpart of the seating portion and the load applied rearward to the upperpart of the backrest portion, as explanatory variables, as in thirdcharacteristic feature of the invention.

[IV]

In order to obtain a seat that causes little fatigue even after a longsitting, it is effective to lessen especially fatigue of the waist inlightening fatigue of the whole body for the driver seated on the seat.

According to a fourth characteristic feature of the present invention,fatigue of the waist of the driver seated on the seat is made an actualdegree of fatigue measured to the driver seated on the seat. Based on aviscoelastic property of muscles of the waist of the driver seated onthe seat, fatigue of the waist of the driver seated on the seat (anactual degree of fatigue measured of the driver seated on the seat) isdetermined.

In this case, the viscoelastic property of the muscles of the waist ofthe driver seated on the seat can be measured by using a vibrator suchas a piezoelectric element. Fatigue of the waist of the driver seated onthe seat may be determined with high accuracy while suppressing ageneration of noise (spike noise). This promotes the reliability of thevehicle driver's fatigue evaluating method.

[V]

According to a fifth characteristic feature of the present invention, avehicle seat evaluating method is provided for evaluating the seat withthe degree of fatigue of the driver seated on the seat calculated by thevehicle driver's fatigue evaluating method described in the foregoingsections [I] to [IV].

According to this, the seat may be evaluated reliably in connection withthe degree of fatigue of the driver seated on the seat. Based on thevehicle seat evaluating method of the fifth characteristic feature ofthe invention, the shape and material of the seat may be changed,thereby to obtain a seat causing a reduced degree of fatigue of thedriver seated on the seat.

[VI]

According to a sixth characteristic feature of the present invention, avehicle seat evaluating apparatus is provided which comprises a firstdetecting device for detecting an amount of rearward deflection of alower part of a backrest portion of a seat, a second detecting devicefor detecting a load applied downward to a front part of a seatingportion of the seat, and a third detecting device for detecting a loadapplied rearward to an upper part of the backrest portion, in a state ofthe driver being seated on the seat; a calculating device forquantitatively calculating a degree of fatigue of the driver seated onthe seat based on detection values of said first, second and thirddetecting devices; and an evaluating device for evaluating the seat bythe degree of fatigue calculated by said calculating device.

According to this, the first, second and third detecting devices and thecalculating device realizes a calculation of the degree of fatigue ofthe driver seated on the seat, free from the subject's subjectivity andwithout noise (spike noise) as described in the foregoing section [I].The seat may be evaluated reliably in connection with the degree offatigue of the driver seated on the seat.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a side elevation of a vehicle seat evaluating apparatus;

FIG. 2 is a perspective view showing a state where load sensors and adeflection sensor of the vehicle seat evaluating apparatus are attacheda seat;

FIG. 3 is a block diagram showing a controller and so on of the vehicleseat evaluating apparatus;

FIG. 4 is perspective views showing states of the vehicle seatevaluating apparatus detecting loads applied rearward to an upper range,an intermediate range and a lower range of a backrest of the seat, loadsapplied downward to a front range, an intermediate range and a rearrange of a seating portion, amounts of rearward deflection in an upperposition, an intermediate position and a lower position of the backrest,and amounts of downward deflection in a front position, and intermediateposition, and a first and a second rear positions of the seatingportion;

FIG. 5 is a view showing changes in the vibration frequency of apiezoelectric element in time of detecting a viscoelastic property ofthe muscles in a subject's waist in a vehicle driver fatigue evaluatingmethod;

FIG. 6 is a view showing a flow of the first half of the vehicledriver's fatigue evaluating method;

FIG. 7 is a view showing a flow of the second half of the vehicledriver's fatigue evaluating method;

and FIG. 8 is a view showing a flow of a vehicle seat evaluating method.

BEST MODE FOR CARRYING OUT THE INVENTION

[1]

The first half of a vehicle driver's fatigue evaluating method forquantitatively calculating a degree of fatigue A of a driver sitting ona seat 1 will be described with reference to FIGS. 4 and 6.

As shown in FIG. 4(a), the seat 1 constructed of pads of predeterminedshape and predetermined material has a plurality of pressure sensors(not shown) arranged in each of an upper range 2 a, an intermediaterange 2 b and a lower range 2 c of a backrest portion 2 of the seat 1,and a front range 3 a, an intermediate range 3 b and a rear range 3 c ofa seating portion 3 of the seat 1. As shown in FIG. 4(b), the same seat1 has a deflection sensor (not shown) arranged in each of an upperposition 2 d, an intermediate position 2 e and a lower position of 2 fof the backrest portion 2 and a front position 3 d, an intermediateposition 3 e and a first and a second rear positions 3 f and 3 g of theseating portion 3.

First, a subject is kept at rest on a relax seat (not shown) differentfrom the above seat 1 for a first predetermined time T1 (e.g. for 15minutes) (step S1). Then, as described in [3] hereinafter, aviscoelastic property K1 (details will be described hereinafter) of themuscles the subject's waist is measured (step S2).

Next, the subject is asked to sit on the above seat 1 (step S3).Immediately after the subject sits down on the seat 1, measurements aretaken through the pressure sensors of a load B2 a applied rearward tothe upper range 2 a of the backrest portion 2, a load B2 b appliedrearward to the intermediate range 2 b of the backrest portion 2, a loadB2 c applied rearward to the lower range 2 c of the backrest portion 2,a load B3 a applied downward to the front range 3 a of the seatingportion 3, a load B3 b applied downward to the intermediate range 3 b ofthe seating portion 3, and a load B3 c applied downward to the rearrange 3 c of the seating portion 3.

In this case, regarding the detection values of the plurality ofpressure sensors arranged in the upper range 2 a of the backrest portion2, for example, an average of the plurality of detection values isregarded as the load B2 a applied rearward to the upper range 2 a (upperpart) of the backrest portion 2. Similarly, the load B2 b appliedrearward to the intermediate range 2 b (intermediate part) of thebackrest portion 2, the load B2 c applied rearward to the lower range 2c (lower part) of the backrest portion 2, the load B3 a applied downwardto the front range 3 a (front part) of the seating portion 3, the loadB3 b applied downward to the intermediate range 3 b (intermediate part)of the seating portion 3 and the load B3 c applied downward to the rearrange 3 c (rear part) of the seating portion 3 are determined (step S4).

Immediately after the subject sits down on the seat 1, measurements aretaken through the deflection sensors of an amount of rearward deflectionC2 d in the upper position 2 d (upper part) of the backrest portion 2,an amount of rearward deflection C2 e in the intermediate position 2 e(intermediate part) of the backrest portion 2, an amount of rearwarddeflection C2 f in the lower position 2 f (lower part) of the backrestportion 2, an amount of downward deflection C3 d in the front position 3d (front part) of the seating portion 3, an amount of downwarddeflection C3 e in the intermediate position 3 e (intermediate part) ofthe seating portion 3, an amount of downward deflection C3 f in thefirst rear position 3 f (first rear part) of the seating portion 3, andan amount of downward deflection C3 g in the second rear position 3 g(second rear part) of the seating portion 3 (step S5). The loads B2 a-B3c and amounts of deflection C2 d-C3 g measured are stored as a data file(step S6).

The subject remains seated on the seat 1 after the subject sits down onthe seat 1 until elapse of a second predetermined time T2 (e.g. forthree hours). When the second predetermined time elapses after thesubject sits on the seat 1 (step S7), as described in [3] hereinafter, aviscoelastic property K2 of the muscles of the subject's waist ismeasured (step S8). Then, a ratio (K2/K1) between the viscoelasticproperty K1 of the muscles of the subject's waist measured in the abovestep S2 and the viscoelastic property K2 of the muscles of the subject'swaist measured in step S8 is determined. The ratio (K2/K1) is regardedas an actual degree of fatigue measured of the driver seated on the seat1, and the ratio (K2/K1) is stored as a data file (step S9). Themeasurement concerning the one seat 1 is completed as described above.

Next, the seat 1 is replaced with a seat 1 constructed of pads ofdifferent shape and different material (steps S10 and S11), and the sameoperation as in above steps S1-S9 is carried out. The same operation asin above steps S1-S9 is carried out for plural types of seat 1.

[2]

The second half of the vehicle driver's fatigue evaluating method forquantitatively calculating a degree of fatigue A of a driver sitting ona seat 1 will be described with reference to FIG. 7.

As described in preceding section [1], when the data file of loads B2a-B3 c and amounts of deflection C2 d-C3 g and the data file of ratio(K2/K1) have been obtained, a multiple regression analysis is carriedout with the loads B2 a-B3 c and amounts of deflection C2 d-C3 g servingas explanatory variables and the ratio (K2/K1) as response variable.

First, a desired number of explanatory variables to be used are selectedfrom the data file of loads B2 a-B3 c and amounts of deflection C2 d-C3g (step S12). Next, a regression coefficient of multiple regressionanalysis is calculated by using the selected explanatory variables andthe well-known algorithm of multiple regression analysis (step S13).Then, a contribution of a multiple regression formula obtained in stepS13 is calculated, and the multiple regression formula is tested (stepS14). While selecting suitable explanatory variables from the pluralityof explanatory variables, these steps of multiple regression analysis,i.e. step S12 to step S14, are repeated for each group of selectedexplanatory variables (step S15).

As noted hereinbefore, various methods are known as methods of selectingoptimal explanatory variables from a plurality of explanatory variables.A desired method may be adopted, for example, from among a round robinmethod for examining regression models of all combinations of theplurality of explanatory variables, a forward selection method foradding one explanatory variable after another, starting with a state ofincluding no explanatory variable, a backward elimination method forsubtracting one explanatory variable after another, starting with astate of including all the explanatory variables, and a sequentialmethod for varying the number of explanatory variables.

When the multiple regression analysis based on the selection ofconceivable explanatory variables is completed, a multiple regressionformula with the highest contribution is specified from the results ofthe multiple regression analysis. This multiple regression formula isset as operational expression for the vehicle driver's fatigueevaluating method (step S16).

The contribution of the multiple regression formula is the highestwhere, regarding the data file collected in [1], the amount of rearwarddeflection C2 f in the lower position 2 f (lower part) of the backrestportion 2, the load B3 a applied downward to the front range 3 a (frontpart) of the seating portion 3 and the load B2 a applied rearward to theupper range 2 a (upper part) of the backrest portion 2 are set asexplanatory variables, and the degree of fatigue A of the driver seatedon the seat 1 is set as the ratio (K2/K1) between the viscoelasticproperty K1 of the muscles of the subject's waist measured in the abovestep S2 and the viscoelastic property K2 of the muscles of the subject'swaist measured in step S8 as response variable.

Consequently, the operational expression for this multiple regressionformula is;A(K2/K1)=D1·C2f+D2·B3a+D3·B2a+D4.Coefficient D1, D2, D3 and D4 are, for example, D1=−0.0061, D2=−0.0246,D3=+0.0237, and D4=+1.4076. In the present invention, D1-D4 are notnecessarily limited to the above numerical values. In the case of theabove operational expression, R²=0.46 has been obtained as coefficientof determination R² (square of the coefficient of multiple correlationR), i.e. a contribution. That is, although the amount of rearwarddeflection C2 f in the lower position of 2 f of the backrest portion 2,the load B3 a applied downward to the front range 3 a of the seatingportion 3 and the load B2 a applied rearward to the upper range 2 a ofthe backrest portion 2 greatly influence the degree of fatigue A of thedriver seated on the seat 1, the present invention can obtainappropriately the degree of fatigue A of the driver seated on the seat.[3]

Next, the viscoelastic property K1 of the muscles of the subject's waistmeasured in the above step S2 described in the foregoing section [1] andthe viscoelastic property K2 of the muscles of the subject's waistmeasured in step S8 will be described.

A piezoelectric element is used as sensor (vibrator). The piezoelectricelement is applied to the subject's waist, for example to the partbetween the third lumbar and fourth lumbar. Next, an operation iscarried out to increase pressure on the piezoelectric element gradually,and when the pressure for the piezoelectric element reaches apredetermined value, to decrease pressure on the piezoelectric elementgradually. Variations in the vibration frequency of the piezoelectricelement occurring during this period are detected.

This state is shown in FIG. 5. The vertical axis in FIG. 5 representsvariations in the vibration frequency (hertz Hz) of the piezoelectricelements, while the horizontal axis in FIG. 5 represents pressure (gramforce gf) on the piezoelectric element. In step S2, as shown in a solidline L1 in FIG. 5, when the piezoelectric element is applied to thesubject's waist and pressure on the piezoelectric element is increasedgradually, the vibration frequency of the piezoelectric element lowersgradually from a predetermined vibration frequency. When the pressure onthe piezoelectric element becomes about 500 gf, the vibration frequencyof the piezoelectric element becomes about −230 Hz. When the pressure onthe piezoelectric element is gradually decreased from about 500 gf, thevibration frequency of the piezoelectric element, after stabilizingaround −230 Hz for a while, quickly returns to the predeterminedvibration frequency.

In this case, a difference Δf1 is measured between the vibrationfrequency of the piezoelectric element when the pressure on thepiezoelectric element on the increase reaches 200 gf and the vibrationfrequency of the piezoelectric element when the pressure on thepiezoelectric element on the decrease reaches 200 gf, and the differenceΔf1 is regarded as the viscoelastic property K1 of the muscles of thesubject's waist. The above solid line L1 shown in FIG. 5 varies withsubjects. A different subject results in a different vibration frequencyof the piezoelectric element at the time when the pressure on thepiezoelectric element reaches about 500 gf.

In step S8, as shown in a long dashed short dashed line L2 in FIG. 5,when the piezoelectric element is applied to the subject's waist and thepressure of the piezoelectric element is increased gradually, thevibration frequency of the piezoelectric element lowers gradually fromthe predetermined vibration frequency. When the pressure on thepiezoelectric element is about 500 gf, the vibration frequency of thepiezoelectric element becomes about −180 Hz. When the pressure of thepiezoelectric element is gradually decreased from about 500 gf, thevibration frequency of the piezoelectric element, after stabilizingaround −180 Hz for a while, quickly returns to the predeterminedvibration frequency.

A difference Δf2 in this case is regarded as the viscoelastic propertyK2 of the muscles of the subject's waist. The above long dashed shortdashed line L2 shown in FIG. 5 varies with subjects. A different subjectresults in a different vibration frequency of the piezoelectric elementat the time when the pressure on the piezoelectric element reaches about500 gf.

As described above, the difference Δf1 is regarded as the viscoelasticproperty K1 of the muscles of the subject's waist, and the differenceΔf2 as the viscoelastic property K2 of the muscles of the subject'swaist. A ratio (Δf2/Δf1) between the difference Δf1 and difference Δf2is regarded as an actual degree of fatigue measured of the driver seatedon the seat 1. This actual degree of fatigue is used as the responsevariable in the foregoing section [2], to calculate the degree offatigue A of the driver seated on the seat 1.

[4]

Next, a vehicle seat evaluating apparatus will be described, whichapparatus uses the vehicle driver's fatigue evaluating method describedin foregoing sections [1]-[3].

FIG. 1 shows the vehicle seat evaluating apparatus which includes a base4 supporting a seat 1 to be evaluated, and a vibrating mechanism 5 forapplying vibrations in various running states of a vehicle to the base 4(which is capable of applying vibrations in vertical directions, foreand aft directions and transverse directions to the base 4). The base 4has a steering wheel 6, an accelerator pedal 7 and a brake pedal 8. Adisplay 9 and a controller 10 are arranged forwardly of the base 4.

As shown in FIG. 2, soft load sensors 11 and 12 in sheet form areprovided with numerous pressure sensors (not shown) arranged atpredetermined intervals. A thin belt-like object 13 made of cloth isconnected to the load sensor 12. The belt-like object 13 has adeflection sensor 14.

As shown in FIGS. 1 and 3, the controller 10 has a microcomputer actingas a core element thereof. Connected to the controller 10 through an I/Ointerface 15 are the load sensors 11 and 12, the deflection sensor 14, asteering signal generator 16 for generating signals based on operationof the steering wheel 6, an accelerator pedal signal generator 17 forgenerating signals based on depression of the accelerator pedal 7, abrake pedal signal generator 18 for generating signals based ondepression of the brake pedal 8, a control input device 19 such as akeyboard, the vibrating mechanism 5, the display 9 and a printer 20.

As shown in FIG. 3, the controller 10 includes a running conditionsetting unit 21 for setting running conditions based on the signals ofthe control input device 19, steering signal generator 16, acceleratorpedal signal generator 17 and brake pedal signal generator 18, avibration control unit 22 for causing the vibrating mechanism 5 togenerate vibrations according to the running conditions set by therunning condition setting unit 21 and the signals of the steering signalgenerator 16, accelerator pedal signal generator 17 and brake pedalsignal generator 18, a detection value processing unit 23 for processingdetection values of the load sensors 11 and 12 and deflection sensor 14,a fatigue degree operating unit 24 for calculating a degree of fatigue Aof the driver seated on the seat 1 based on results of processing by thedetection value processing unit 23, a seat evaluating unit 25 forevaluating the seat 1 based on the degree of fatigue A calculated by thefatigue degree operating unit 24, and a running scene generating unit 26for causing the display 9 to display running scenes according to thesignals of the running conditions set by the running condition settingunit 21, steering signal generator 16, accelerator pedal signalgenerator 17 and brake pedal signal generator 18.

[5]

Next, a method of evaluating the seat 1 (vehicle seat valuating method)will be described with reference to FIG. 8, which method uses thevehicle seat evaluating apparatus described in the preceding section[4].

As shown in FIGS. 1 and 2, the seat 1 to be evaluated is provided, andthe seat 1 is attached to the base 4 (step S21). The load sensor 11 isattached to a front part of a seating portion 3, and the load sensor 12is attached to an upper part of a backrest portion 2. As described inthe preceding section [4], the thin belt-like object 13 made of cloth isconnected to the load sensor 12. The belt-like object 13 has thedeflection sensor 14. When the load sensor 12 is attached to the upperpart of the backrest portion 2 as noted above, the deflection sensor 14is located on the lower part of the backrest portion 2 (step S22).

Running conditions (high-speed running state, urban area running state,off-road running state, etc.) are set and inputted from the controlinput device 19 (step S23). When a subject sits down on the seat 1 (stepS24), an evaluation of the seat 1 is started. When the evaluation of theseat 1 is started, the vibrating mechanism 5 generates vibrationsaccording to the running conditions set in step S23 and the signals ofthe steering signal generator 16, accelerating signal generator 17 andbrake pedal signal generator 18, and running scenes are displayed on thedisplay 9 (step S25).

During this period, upon lapse of each predetermined time, thedeflection sensor 14 detects an amount of rearward deflection C2 f inthe lower part of the backrest portion 2, the load sensor 11 detects aload B3 a (an average of detection values of the numerous pressuresensors included in the load sensor 11) applied downward to the frontpart of the seating portion 3, and the load sensor 12 detects a load B2a (an average of detection values of the numerous pressure sensorsincluded in the load sensor 12) applied rearward to the upper part ofthe backrest portion 2 (step S26).

In this case, in step S26, averages of detection values obtained uponlapse of each predetermined time are regarded as the amount of rearwarddeflection C2 f in the lower part of the backrest portion 2, the load B3a applied downward to the front part of the seating portion 3, and theload B2 a applied rearward to the upper part of the backrest portion 2,or detection values detected immediately after an end are regarded asthe amount of rearward deflection C2 f in the lower part of the backrestportion 2, the load B3 a applied downward to the front part of theseating portion 3 and the load B2 a applied rearward to the upper partof the backrest portion 2.

Based on the above amount of rearward deflection C2 f in the lower partof the backrest portion 2, the load B3 a applied downward to the frontpart of the seating portion 3 and the load B2 a applied rearward to theupper part of the backrest portion 2, the degree of fatigue A of thedriver seated on the seat 1 is calculated by the vehicle driver'sfatigue evaluating method (operational expression) described in theforegoing sections [1]-[3] (steps S27 and S28). When changing runningconditions (high-speed running state, urban area running state, off-roadrunning state, etc.) for the same seat 1 (step S29), running conditionsare inputted from the control input device 19 (step S23), and the abovesteps S25-S28 are repeated. Then, evaluation results of the seat 1 (suchas the degree of fatigue A of the driver seated on the seat 1) areoutputted to the printer 20 (step S30).

INDUSTRIAL UTILITY

Based on the vehicle seat evaluating method, the shape and material of aseat may be changed, thereby to obtain a seat producing a reduced degreeof fatigue of the driver seated on the seat.

1-6. (canceled)
 7. A vehicle driver's fatigue evaluating method forquantitatively calculating a degree of fatigue of a driver seated on aseat based on an amount of rearward deflection of a lower part of abackrest portion of the seat, a load applied downward to a front part ofa seating portion of the seat, and a load applied rearward to an upperpart of the backrest portion, in a state of the driver being seated onthe seat.
 8. The vehicle driver's fatigue evaluating method as definedin claim 7, wherein the degree of fatigue of the driver seated on theseat is calculated quantitatively by using an operational expressiondetermined by a statistical technique.
 9. The vehicle driver's fatigueevaluating method as defined in claim 8, wherein said operationalexpression is obtained by a multiple regression analysis with the amountof rearward deflection of the lower part of the backrest portion, theload applied downward to the front part of the seating portion and theload applied rearward to the upper part of the backrest portion regardedas explanatory variables, and an actual degree of fatigue measured ofthe driver seated on the seat as a response variable.
 10. The vehicledriver's fatigue evaluating method as defined in claim 9, wherein saidactual degree of fatigue is derived from a viscoelastic property ofwaist muscles of the driver seated on the seat.
 11. A vehicle seatevaluating apparatus comprising: a first detecting device for detectingan amount of rearward deflection of a lower part of a backrest portionof a seat, a second detecting device for detecting a load applieddownward to a front part of a seating portion of the seat, and a thirddetecting device for detecting a load applied rearward to an upper partof the backrest portion, in a state of the driver being seated on theseat; a calculating device for quantitatively calculating a degree offatigue of the driver seated on the seat based on detection values ofsaid first, second and third detecting devices; and an evaluating devicefor evaluating the seat by the degree of fatigue calculated by saidcalculating device.
 12. A vehicle seat evaluating method for evaluatinga seat with a degree of fatigue calculated by a vehicle driver's fatigueevaluating method for quantitatively calculating a degree of fatigue ofa driver seated on the seat based on an amount of rearward deflection ofa lower part of a backrest portion of the seat, a load applied downwardto a front part of a seating portion of the seat, and a load appliedrearward to an upper part of the backrest portion, in a state of thedriver being seated.
 13. The vehicle seat evaluating method as definedin claim 12, wherein the degree of fatigue of the driver seated on theseat is calculated quantitatively by using an operational expressiondetermined by a statistical technique.
 14. A vehicle seat evaluatingmethod as defined in claim 12, wherein said operational expression isobtained by a multiple regression analysis with the amount of rearwarddeflection of the lower part of the backrest portion, the load applieddownward to the front part of the seating portion, and the load appliedrearward to the upper part of the backrest portion regarded asexplanatory variables, and an actual degree of fatigue measured of thedriver seated on the seat as a response variable.
 15. A vehicle seatevaluating method as defined in claim 14, wherein said actual degree offatigue is derived from a viscoelastic property of waist muscles of thedriver seated on the seat.